Wood in River Rehabilitation and Management


By Tim B. Abbe, Andrew P. Brooks, and David R. Montgomery

Wood induces hydraulic, morphologic, and textural complexity into fluvial systems in forested regions around the world. Snags and logjams can create complex networks of channels and wetlands across entire river valleys and historically posed a significant obstacle to navigation. The clearing of wood from rivers and riparian forest land along streams and rivers reduced or eliminated the supply of wood into rivers in many regions of the world. Ecological restoration of fluvial environments increasingly includes the placement of wood. But few guidelines exist on appropriate methods for emulating natural wood accumulations, where and how to place wood, its longevity, the hydraulic and geomorphic consequences of wood, and how to manage systems where wood is reintroduced. Important issues to understand when placing wood in rivers include the watershed and reach-scale context of a project, the hydraulic and geomorphic effects of wood placements, possible changes in wood structures over time, and how it may impact human infrastructure and safety. Engineered logjams constructed in Washington, USA and New South Wales, Australia offer examples of how wood reintroduction can be engineered without the use of artificial anchoring to form stable in-stream structures as part of efforts to rehabilitate fluvial ecosystems and provide ecologically sensitive means to treat traditional problems such as bank stabilization and grade control.